Device for gripping and holding and object in a contactless manner

ABSTRACT

A device is proposed for the contactless grasping and holding of an object ( 1 ) from a direction (z) directed at least partially in the direction (z) of the force of gravity (F), using a holding element ( 3 ) situated counter to the direction (z) of the force of gravity (F), at least partially above the object ( 1 ) and at a distance from the latter, which to the greatest extent possible avoids the carrying off or migrating of particles that are possibly present. According to the present invention this is achieved in that the holding element ( 3 ) is designed as a vibrating holding element ( 3 ) for generating levitation waves.

[0001] The present invention relates to a device for the contactlessgrasping and holding of an object from a direction aligned in thedirection of the force of gravity, according to the definition of thespecies in Claim 1.

BACKGROUND INFORMATION

[0002] In the manufacturing of semiconductors, for example, andmicrosystems technology, numerous components are furnished at theirsurface with structures that are sensitive to the touch. Suchcomponents, among other things, have movable, filigree etchingstructures, such as diaphragms, reeds or jumpers, possibly as componentsfor pressure sensors or acceleration sensors. In order to avoidimpairment, this requires contactless grasping and holding of thecomponent.

[0003] In addition, on account of a mechanical contact of grasping withthe component surface, particles could be abraded or generated, andcould possibly be carried off onto the component surface, which has adisadvantageous effect on the manufacturing yield.

[0004] Furthermore, components having sensitive surfaces or surfacecoatings, such as freshly lacquered components or the like in almost alltechnical fields, may likewise be grasped and held in a contactlessmanner.

[0005] In the case of certain applications, the component may only begrasped and held from above, i.e. the direction aligned with thedirection of the force of gravity, for instance, when grasping acomponent that was laid down on a storage area or a transportationdevice, or when mounting or assembling the component on a specifiedobject or storing it. Such cases of application exist, for example, inthe bonding of semiconductor disks, or during so-called wafer bonding,in which case the corresponding component is to be applied accuratelyand with a defined contact pressure to a structural element withoutdamaging corresponding structures or surfaces. In the case of theseapplications, no grasping or holding devices may be used which hold orgrip the component from two opposite sides.

[0006] Such a one-sided, contactless grasper and holder is known, forinstance, from document DE 198 06 306. This document describes a devicein which the respective object is positioned in the direction of theforce of gravity, in a contactless manner, below a holding element,using pneumatic tractive forces and pressure forces.

[0007] However, this has the disadvantage that, in order to generate thepneumatic tractive and pressure forces, gas flows out from appropriateoutflow orifices or is aspirated in inflow orifices, which may lead toparticles being carried off, and thus to a loss in manufacturing yield.

OBJECT AND ADVANTAGES OF THE INVENTION

[0008] By contrast, it is the object of the present invention to proposea device for the contactless grasping and holding of an object from adirection, preferably a direction aligned with the direction of theforce of gravity, which to the greatest extent avoids the carrying offor migrating of particles that may possibly be present.

[0009] Starting from a device of related art of the type indicated inthe introduction, this object is attained by the characterizing featuresof Claim 1.

[0010] The measures indicated in the dependent claims permitadvantageous embodiments and further developments of the presentinvention.

[0011] In this regard, the device according to the present invention hasthe distinction that the holding element is designed as a vibratingholding element for generating levitation waves.

[0012] Surprisingly, in practice it turns out that just one holdingelement positioned counter to the direction of gravity above the object,i.e. counter to the direction of sound propagation, which, inparticular, generates acoustical levitation waves, is able to grasp andhold an object at an advantageous distance apart. In this instance, nosecond holding element has to be positioned on the side of the objectlying opposite the vibrating holding element, such as, for example, areflector or a second vibrating holding element for generating standingwaves between the two holding elements.

[0013] Beyond that, it also turned out that the object to be held andgrasped may have any desired, particularly three-dimensional form orgeometry. Furthermore, using a device according to the presentinvention, floppy parts such as foils, diaphragms, papers, textiles orthe like, fragile components such as glass elements, comparably thinsemiconductor components or similar items, as well as surface-coatedobjects or components, having structures sensitive to the touch, may begrasped, held and positioned at their surface.

[0014] At this time, devices are already known which are able to holdand transport objects with the aid of the physical principle ofso-called near field levitation (cf, for example, U.S. Pat. No.5,810,155 or DE 199 16 922). However, it is common to these andcomparable devices that the object to be held or transported ispositioned above the vibrating holding element, i.e. that the vibratingholding element is situated below the object in the direction ofgravity.

[0015] The technical world assumed up to now, among other things, thatthe object may only be pressed away from the vibrating supportingelement because of the sound pressure of the levitation waves. In regardto this, known devices using the principle of acoustical near fieldlevitation have been provided exclusively for applications in whichextending below the object is implementable.

[0016] The possibility of extending below the object to be grasped andheld is not necessary when using a device according to the presentinvention. As a consequence, according to the present invention it ispossible to grasp and lift up an object, in a contactless manner, at apick-up location exclusively from one side or rather from above,possibly to transport it over a certain distance and subsequently toposition it at a deposit location designed in any desired manner. Afterpublication of the present invention, one may assume that the technicalworld will subsequently supply the exact explanations required therefor.

[0017] The vibrating holding element is advantageously designed fordecoupling ultrasound waves having frequencies between 16 kHz and 1GHz., especially between 20 kHz and 40 kHz. With the aid of thismeasure, advantageous holding performances or rather holding forces maybe implemented for grasping and holding the object. In an advantageousmanner, adaptation of the frequencies is provided in dependence upon theobject to be grasped and held. With this concept in mind, above all, anadvantageous adaptation to the required procedural dynamics of eachrespective application case, such as the so-called “pick and place”task, may be implemented.

[0018] In one particular refinement of the present invention, a supportsurface of the holding element situated opposite the object, is adaptedto the surface section of the object. In this case, the surface sectionof the object may have any desired, preferably three-dimensional shape,to which the support surface of the holding element is to be adapted.

[0019] A projection of the object onto a plane that is aligned nearlyperpendicularly to the force of gravity may possibly correspond to thegreatest extent possible to a projection of the support surface of theholding element of the corresponding plane. Hereby, in an advantageousmanner, among other things, rotational securing or centering of theobject is implemented on account of advantageous edge effects.Alternatively to this, the projection of the support surface of theholding element may be designed to be smaller than the projection of thesurface section of the object that is positioned opposite to it.

[0020] These variants of the present invention above all make possibleadvantageous grasping and/or positioning of the object from and/or intoa gap whose area largely corresponds to the respective projection of theobject. For example, electrical or micromechanical components may bepositioned in a gap between other components on a substrate, the gapapproximately corresponding to the dimensions of the component. Therebya comparatively high component density may possibly be implemented onappropriate substrates, which may lead to an advantageousminiaturization of the corresponding products.

[0021] For example, the three-dimensional adaptation of the supportsurface to the surface section takes place in such a way that thesupport surface, in addition to an appropriate distance from the object,is to be designed almost as the negative shape of the surface section.Thus, for example, in the case of a sphere as the object to be held, thesupport surface of the holding element may possibly be designed as aspherical half shell having a slightly larger diameter than the diameterof the sphere.

[0022] In addition, more complex three-dimensionally designed objects,such as freshly lacquered body parts in the automotive industry or thelike, may be grasped or held in a contactless manner, and possibly betransported from a pick-up location and positioned and pressed onto asupport, with the aid of support elements having an appropriatelyadapted complex three-dimensional support surface according to thepresent invention.

[0023] In an advantageous manner, an area of the surface section ispositioned transversely to a vibrational direction of the supportsurface in this area. This ensures that the running direction of thelevitation waves is aligned perpendicularly to the region of the object,which leads to an advantageous pick-up in the holding performance, andthus, comparatively heavy objects may be held or grasped.

[0024] In one preferred variant of the present invention, the supportsurface of the holding element has at least one opening of at least onerecess of the holding element. In this connection, the opening and/orthe recess may have any cross section or any desired shape.

[0025] While carrying out this measure, it was observed that greaterholding forces for contactless grasping and holding the object may beimplemented. This observation is based on the assumption that, in thisprocess, the gas volume present in the recess is, among other places,sucked into the gap between the object and the holding element, so thatunderpressure may be created in the recess, which draws the objectagainst the holding element or rather against the direction of the forceof gravity. Thereby, particularly, an improved procedural dynamics ofthe device is implemented with respect to the object held. For instance,in this method, the holding element may achieve greater accelerations orprocedural speeds.

[0026] Basically, the depth of the recess should be designed to begreater than the width of the opening, whereby the recess has acomparatively large volume and, at the same time, a comparatively largesupport surface may be implemented. The recess should possibly bedesigned to be open at its end opposite to the opening of the supportsurface.

[0027] The recess is formed preferably as a bore, especially a blind endbore. A corresponding bore may be applied in an advantageous manner tothe holding element without great effort, so that the manufacturing costfor a holding element having one or more recesses may be minimized.

[0028] In one particular further development of the present invention,at least one additional force generating unit is provided for generatingadditional force directed counter to the force of gravity. For this, forexample, magnetic, electrostatic, electrodynamic, pneumatic orcomparable forces may be generated using the appropriate forcegenerating units. In this connection, too, the force generating unit isadvantageously positioned counter to the direction of gravity, above theobject.

[0029] The force generating unit is preferably designed as a pressuregenerating unit, above all as an underpressure generating unit,particularly having at least one suction element for drawing in theobject. Using this measure, a contactless grasping and holding of theobject may be implemented, with the aid of tractive forces directedcounter to gravity, which leads to a further improvement of theprocedural dynamics of the device in the case of an object heldaccording to the present invention. For certain application cases, in anadvantageous way a plurality of aspirating elements may be used so as toincrease the tractive forces.

[0030] The suction element for drawing in the object may, for example,be designed as a ring nozzle positioned around the holding element, as asimple suction nozzle positioned on the holding element and/or as asuction nozzle at a distance from the holding element. In the last-namedcase, this is particularly advantageous if the surface section of theobject is substantially larger than the support surface of the holdingelement.

[0031] In addition, the suction element may be integrated into theholding element. The pressure generating unit is preferably situated atthe open end of the recess that lies opposite the opening of the supportarea. Thereby, in a relatively simple manner, the integration of thesuction element into the holding element may be implemented, since therecess is simultaneously used as the suction element.

[0032] The pressure generating unit is preferably connected to thevibrating holding element by the use of proven vibration-insulatedconnectors, such as to the open end of the recess, or to especiallyprovided suction elements vibrating along with the holding element.

[0033] In one preferred variant of the present invention, a fixing unitis provided for fixing the object transversely to the direction ofgravity. By doing this, both a lateral centering and a rotationalsecuring of the floating object may be implemented, so that, forexample, a lateral sliding off of the object, caused, for example, byforces of inclination or acceleration, is effectively prevented. Thelateral centering and/or rotational securing may be carried out using aplurality of possibilities already known. For instance, fixed or movablestops or the like may be used.

[0034] A fixing unit is used in an advantageous manner, which isdesigned for contactless fixing of the object. In this variant of thepresent invention, one or more fixing elements are used, for example,which are designed as a suction nozzle and/or a pressure nozzle or thelike.

[0035] Advantageously, a vibrating fixing element of the fixing unit isprovided for generating levitation waves. In this connection, the fixingelement may be designed corresponding to the holding element forgenerating levitation waves, possibly according to the principle of nearfield levitation. In addition, fixing with the aid of vibrating fixingelements may be implemented, which makes possible the formation of astanding wave between the fixing elements.

[0036] In a preferred manner, the vibrating holding element may bedesigned at the same time as a fixing element, one or more fixingelements, for example, being integrated into the holding element and/or,with the aid of integrated fixing elements, the holding element isdesigned for the formation of different amplitudes of the holdingelement which decrease toward the edge of the holding element.

[0037] In general, with the aid of the adaptation of the support surfaceof the holding element, at the surface section of the object, a fixingof the object transversely to the direction of gravity may beimplemented at the same time. During experiments it has been shown thata contactless self-centering of the object occurs in response toextensive conformity in the geometry, particularly of sections of theedge areas, of the support area of the holding element to the geometry,particularly sections of the edge regions of the surface section of theobject. Because of this, one may possibly do without additional fixingelements, which especially reduces the construction cost of the deviceaccording to the present invention.

[0038] In one preferred variant of the present invention, a plurality ofholding elements and/or fixing elements is provided. With the aid ofthis measure, for example, several holding elements each having acomparatively small support surface, may be distributed particularlyevenly over the surface section of the object facing towards the holdingelements. In general, a plurality of vibration sources may be positionedat one and/or several holding elements.

[0039] These variants make possible particularly grasping and holdingrelatively large objects, which may possibly have a comparativelycomplex three-dimensional geometry, as well as possibly lateralcentering of the object. Above all, for the lateral centering of theobject, a plurality of holding elements may advantageously be situatedin corner or edge regions of the object. In this connection, preferablyextensive agreement of sections of the edge regions of the holdingelements and of the object is provided.

[0040] In the case of these variants, the holding elements and vibrationsources are to be positioned in such a way that the vibrationaldirection of the holding element, in the region of the surface sectionlying opposite the object, is aligned perpendicular with respect to thisregion. Thereby, in an especially simple manner, the adaptation of thesupport surfaces, above all to complex surface sections of the object,may be implemented.

[0041] In addition, in an advantageous manner, a suction element may bepositioned between several vibrating holding elements. If necessary,even a plurality of suction elements may be provided for the use of oneor more holding elements.

[0042] In general, it is also conceivable that possibly several holdingelements and/or fixing elements may be positioned along a predefinedtransportation route, the object being positioned in the direction ofgravity below the holding element(s), freely floating according to thepresent invention. In this connection, the object is advantageouslyinduced to move along the transportation route using proven and knownmethods. Advantageously, the movement of the object is realized usingsuction elements arranged at an angle to the transportation direction.

[0043] Alternatively to this, the holding element is designed, movableespecially vertically and/or horizontally with the aid of at least onelifting arm and/or tilting arm, so that in an advantageous manner theobject may execute a defined change in position from a pick-up locationto a lay-down location.

[0044] Generally, the feedback of the object or holding element to thevibration generator, for example, the power consumption, may beascertained and evaluated using an appropriate evaluation unit, so thathereby in an advantageous manner it may be determined whether the objectis being held by the device or not, and how much force is being appliedto the object in a contactless manner. This measure makes possible anadvantageous control of grasping and holding, as well as of positioningof the object and, for example, of the forces when pressing on. In apreferred manner, the power consumption of the object is ascertained byrecording an electrical voltage and an electrical current of apiezoelectric vibration generating unit.

EXEMPLARY EMBODIMENT

[0045] An exemplary embodiment of the invention is shown in the drawingsand is clarified more precisely in the following with reference to thefigures. The figures show:

[0046]FIG. 1 a schematic view of the device according to the presentinvention,

[0047]FIG. 2 a schematic cross section through a holding elementaccording to the present invention having an integrated suction boring,

[0048]FIG. 3 a schematic cross section through a further holding elementaccording to the present invention having a blind-end bore,

[0049]FIG. 4 different variants shown in perspective of further holdingelements according to the present invention,

[0050]FIG. 5 various schematically shown devices according to thepresent invention having contactless ultrasound lateral centering,

[0051]FIG. 6 various schematically shown devices according to thepresent invention, having contactless aerostatic lateral centering,

[0052]FIG. 7 various schematically shown devices according to thepresent invention, having mechanical contact lateral centering,

[0053]FIG. 8 various working steps in a pick-up procedure or a lay-downprocedure using a device according to the present invention, shownschematically.

[0054] In FIG. 1 a schematic design of a device according to the presentinvention is shown, for the contactless grasping and holding of anobject 1, such as a chip 1. However, in the case of object 1, otherfragile, floppy and/or surface sensitive components may be involved,such as paper, textiles, diaphragms, foils, microsystem technologycomponent parts, semiconductor elements, toxic and contaminated objectsor objects otherwise dangerous to human beings, above all of thechemical or pharmaceutical industry, comparatively hot and/or coldelements, freshly lacquered objects, especially in the automotiveindustry, or other technical applications, glass substrates in themanufacturing of flat screens or the like.

[0055] A unit 2 for generating ultrasound vibrations includes for this asonotrode 3, piezo elements 4, connectors 5, a nodal plate 6 as well ascontrol electronics 7.

[0056] Sonotrode 3 is thereby stimulated to vibrate, so that it maygenerate or decouple ultrasound levitation waves for contactlessgrasping and holding chip 1.

[0057] According to the present invention, chip 1 is situated underneathsonotrode 3, in direction z of force of gravity F.

[0058] In the variant of the present invention as in FIG. 1, sonotrode 3has a plurality of bores 8 which open out into a collecting main 9 andare connected to a vacuum pump (not shown in detail) via avibration-insulated connecting line 10. With the aid of a pressuregenerating unit that is not shown in detail, in particular anunderpressure p is generated for generating a pneumatic tractive forcedirected counter to force of gravity F. This pneumatic tractive forceimproves the grasping and holding of chip 1 with the aid of the deviceaccording to the present invention.

[0059] In addition, in FIG. 1 it becomes clear that the device accordingto the present invention is designed for grasping and holding a chip 1,chip 1, for example, being grasped from a support 11 and laid down on itagain without holding elements having to be provided for this purpose onthe side of support 11 lying opposite the device.

[0060] In addition, two mechanical stops 12 are shown in FIG. 1 for thelateral fixing of chip 1. In certain application cases, mechanicaltouching of the edge regions or the sides and/or parts of the undersideof object 1, that is to be grasped and held, may be tolerated, above allbetween lifting it and laying it down.

[0061]FIG. 2 schematically shows a sonotrode 3 a having only a suctionbore 8. Suction bore 8 is connected to a vacuum pump via avibration-insulated connector 5, in a manner not shown in detail.Sonotrode 3 a vibrates, for example, at an ultrasound frequency of 20 to40 kHz, so that a component 14 is to be grasped and held in acontactless manner counter to direction z of force of gravity F, beneathvibrating head 3 a.

[0062]FIG. 3 schematically shows a sonotrode 13 having a blind-end bore15. In a grasping and holding phase, before anything else, according tothe present invention, sonotrode 13 is set to vibrating at a frequencyof 20 to 40 kHz, so that component 14 is held underneath sonotrode 13,as seen in direction z of force of gravity F.

[0063] According to FIG. 4, the most varied shapes or embodimentpossibilities of sonotrodes 17 a, 17 b, 17 c are advantageous. In thisconnection, support surfaces 18 are adapted, for example, to a componentnot shown in detail. Support surfaces 18 closely approximate a surfacesection of a component facing support surface 18, such as a sensor chip.Like support surfaces 18, the sensor chip not shown also has arectangular cross sectional surface. With the aid of this measure, acontactless self-centering, including a rotational securing of thecomponent not shown, is able to be implemented underneath sonotrodes 17a, 17 b, 17 c.

[0064] Basically, the lateral centering of sonotrode 17 c is better thanthat of sonotrode 17 b, and it, in turn, is better than that ofsonotrode 17 a. For this, probably, advantageous edge effects or flowprofiles at the edge of support surfaces 18 are of importance.

[0065] Furthermore, FIG. 4 shows openings 16, to be optionally provided,of recesses not shown, which, for instance, may be designed as bore 8 orblind-end bore 15.

[0066]FIG. 5 shows the most varied methods or rather, devices accordingto the present invention, having contactless ultrasound lateralcentering. In this connection in particular, a device is used having asonotrode 3 following the device as in FIG. 1.

[0067] Compared to the device in FIG. 1, in the variants as in FIG. 5 alateral centering of component 14 is implemented, using a vibratingfixing element 19. In FIG. 5a as well as 5 b, the centering is carriedout according to the principle of acoustical near-field centering,fixing elements 19 being able to be integrated into sonotrode 3, ifnecessary.

[0068] According to FIG. 5c, the centering takes place by holdingcomponent 14 in the first node of the vibrational waves. In FIG. 5d, thefixing of component 14 takes place using a standing wave, not shown, inparticular, two opposite fixing elements 19 being supposed to be used,two vibrating or one vibrating and one reflecting fixing element 19being able to be provided.

[0069] The lateral centering according to FIG. 5e takes place by theBernoulli effects of an outside standing wave, with the aid of fixingelements 19, the latter being able to be integrated into sonotrode 3, ifnecessary.

[0070] According to FIG. 5f, the centering of component 14 may beimplemented with the aid of different amplitudes of sonotrode 3, theamplitudes diminishing radially outwards. Fixing element 19 is, in thisconnection, being integrated in particular in the end region ofsonotrode 3.

[0071]FIG. 6 shows further variants for the contactless centering ofcomponents 14, the centering taking place by using pneumatic blowing-inaccording to FIG. 6a or by self-centering on account of a ring nozzle orby Bernoulli effects.

[0072]FIG. 7 shows mechanically tactile fixing elements 19 for fixingcomponent 14.

[0073]FIG. 8 shows schematically a pick-up procedure and a lay-downprocedure of a component 14, using a device according to the presentinvention. According to FIG. 8a, the device is positioned, according toFIG. 1, over a component 14 which is present in a so-called chip tray,the chip tray forming at the same time support 11 of component 14.

[0074] Subsequently, according to FIG. 8b, component 14 is grasped in acontactless manner using vibrating head 3, and according to FIG. 8c itis lifted from support 11. Almost simultaneously, or rather immediatelythereafter, the centering of component 14 takes place according to FIG.8d, by the moving of stops 12 in direction z and along a direction x, sothat component 14 is secured against slipping sideways.

[0075] In a manner not shown, there follows the transportation of unit2, having component 14, in direction x and/or direction y away fromsupport 11, on to a substrate 20. At a specified location, unit 2 ispositioned above substrate 20, and subsequently there takes place aforce-regulated, contactless assembling of component 14 onto substrate20. In this connection, in an advantageous manner, the progressiveincrease in carrying force counter to direction z is used, in dependence(not shown) on the distance between component 14 and sonotrode 3 forgenerating a contact pressure force, directed onto substrate 20, of froma few milliNewtons to a few 1000 kiloNewtons. Finally, the lifting offof switched-off unit 2 takes place, in direction −z, according to FIG.8f.

What is claimed is:
 1. A device for the contactless grasping and holdingof an object (1, 14) from a direction (z) directed at least partially inthe direction (z) of the force of gravity (F), using a holding element(3, 13, 17) situated counter to the direction (z) of the force ofgravity (F), at least partially above the object (1, 14) and at adistance from the latter, wherein the holding element (3, 13, 17) isdesigned as a vibrating holding element (3, 13, 17) for generatinglevitation waves.
 2. The device as recited in claim 1, wherein thevibrating holding element (3, 13, 17) is designed to generate ultrasoundwaves having frequencies between 16 kHz and 1 GHz.
 3. The device asrecited in one of the preceding claims, wherein a support surface (18)of the holding element situated opposite the object (1, 14) is adaptedto a surface section of the object (1, 14).
 4. The device as recited inone of the preceding claims, wherein an area of the surface section issituated transversely to a vibrational direction (z) of the holdingelement (3, 13, 17) in this area.
 5. The device as recited in one of thepreceding claims, wherein the support surface (18) of the holdingelement (3, 13, 17) has at least one opening (16) of at least one recess(8, 15) of the holding element (3, 13, 17).
 6. The device as recited inone of the preceding claims, wherein the recess (8, 15) is designed as abore (8, 15).
 7. The device as recited in one of the preceding claims,wherein at least one additional force generating unit is provided forgenerating an additional force directed counter to the force of gravity(F).
 8. The device as recited in one of the preceding claims, whereinthe force generating unit is designed as a pressure generating unit. 9.The device as recited in one of the preceding claims, wherein thepressure generating unit has at least one suction element (8) to draw inthe object (1, 14).
 10. The device as recited in one of the precedingclaims, wherein the pressure generating unit is situated at one end ofthe recess (8, 15) lying opposite the opening (16).
 11. The device asrecited in one of the preceding claims, wherein a fixing unit (12, 19)for fixing the object (1, 14) is provided transversely (x, y) to thedirection (z) of the force of gravity (F).
 12. The device as recited inone of the preceding claims, wherein the fixing unit (12, 19) isdesigned for the contactless fixing of the object (1, 14).
 13. Thedevice as recited in one of the preceding claims, wherein a vibratingfixing element (19) of the fixing unit (12, 19) is provided forgenerating levitation waves.
 14. The device as recited in one of thepreceding claims, wherein a plurality of holding elements (3, 13, 17)and/or fixing elements (12, 19) is provided.
 15. A method for thecontactless grasping and holding of an object (1, 14) from a direction(z) directed at least partially in the direction (z) of the force ofgravity (F), using at least one holding element (3, 13, 17) situatedcounter to the direction (z) of the force of gravity (F), at leastpartially above the object (1, 14) and at a distance from the latter,wherein a device as recited in one of the preceding claims is used,having a vibrating holding element (3, 13, 17) for generating levitationwaves.